1. Field of the Invention
The present invention relates to a reproduction apparatus comprising a print unit of at least one print unit comprising print elements for ejecting drops of marking material on a plurality of sheets, the print unit having two ends in a first direction perpendicular to a transport direction of the plurality of sheets, a transport mechanism configured to transport the plurality of sheets towards the print unit in the transport direction, a displacing mechanism configured to displace the sheets in the first direction, and a controller configured to control the print unit the transport mechanism and the displacing mechanism.
Hereinafter the term print unit may be used for convenience reasons, but it should be understood that the term print unit can also be a print unit consisting of several print units. Also, the term print unit can also be a print bar of several print units or several page wide arrays.
The present invention also relates to a method for printing on sheets by a reproduction apparatus according to the present invention.
2. Background of the Invention
Reproduction apparatuses are known which are able to print jobs arriving at the reproduction apparatus via a network or an analogue document via a scanner being part of the reproduction apparatus. Such a job may contain an image and/or text in black-and-white format or in color format. The job entry in the reproduction apparatus may be controlled by the control mechanism, for example a computer, a control unit and/or a processor inside the reproduction apparatus. Also the controller may convert image and/or text data into commands for the print unit to let the printing elements eject marking material at the right spot and the right time on sheets. The job may be printed on sheets which are transported along a print unit in the transport direction, for example inkjet printers. Especially the size of the print unit in the transport direction is usually larger than the distance between two succeeding sheets on the transport mechanism. The distance between two succeeding sheets is small in order to achieve a high productivity of the reproduction apparatus.
A print unit may comprise a plurality of page wide arrays which are mutually aligned. Usually, page wide arrays are relatively heavy and connected via many cables and hose pipes for transport of the marking material, like ink, to the page wide arrays.
If the print unit is stationary, for example a plurality of page wide arrays, the sheets may have a small format in comparison with the size of the print unit. Therefore, not all printing elements of the print unit are used to eject marking material on the sheets, since marking material ejected from outmost printing elements would drop on the transport mechanism, e.g. a transport layer of the transport mechanism underneath the sheets, instead of on the sheets. Outmost printing elements are therefore usually not used when printing on sheets of such a small format. This is disadvantageous, since the outmost nozzles may easily become clogged. Clogging is an important failure mechanism in inkjet printers. To prevent nozzles from clogging, they need to eject a drop of marking material from time to time. When a printing element is clogged, a repair action needs to be carried out, which leads to a decrease of the productivity of the reproduction apparatus.
In the case of a small format of sheets, the ejection of drops of marking material from time to time becomes impossible for outmost printing elements or at least for printing elements at one side of the print unit under which no part of each small format sheet will be transported.